When is the hardware related register is allocated?

[Feng LI]

Hi,

I'm working on a gcc backend, we need to use the information of the
allocated hardware register to generate the code from builtin
functions. But at the context in ix86_expand_builtin, where I could
get the operands which the registers are pseudo registers
(REGNO(op)>FIRST_PSEUDO_REGISTER).

Do you know where could I get the information of the hardware register
and generate assemble code from there?

Thanks,
Feng